University of California - Berkeley

Exposing Photo Manipulation with Inconsistent Reflections

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Abstract

The advent of sophisticated photo editing software has made it
increasingly easier to manipulate digital images. Often visual
inspection cannot definitively distinguish the resulting forgeries
from authentic photographs. In response, forensic techniques have
emerged to detect geometric or statistical inconsistencies that
result from specific forms of photo manipulation. In this paper we
describe a new forensic technique that focuses on geometric
inconsistencies that arise when fake reflections are inserted into a
photograph or when a photograph containing reflections is
manipulated. This analysis employs basic rules of reflective
geometry and linear perspective projection, makes minimal
assumptions about the scene geometry, and only requires the user to
identify corresponding points on an object and its reflection. The
analysis is also insensitive to common image editing operations such
as resampling, color manipulations, and lossy compression. We
demonstrate this technique with both visually plausible forgeries of
our own creation and commercially produced forgeries.